Masking film for protecting sensitive substrates

Abstract

A masking film comprising an adhesion layer that is a blend of a hydrogenated styrene block copolymer and a low density polyethylene. The adhesive layer has an outer adhesive surface configured to contact a substrate. The outer adhesion surface has an average surface roughness Ra of 100 nm to 350 nm and an average peak pitch Sm of 20 [mu] m to 150 [mu] m. The masking film also includes a release layer on a side of the adhesion layer opposite the outer adhesion surface.

Description

[0001] This application is a divisional application based on the Chinese patent application with application number 201980084109.9, application date December 13, 2019, and invention name “Masking film for protecting sensitive substrates”.

[0002] Cross-reference to related applications

[0003] This application claims the benefit of priority to U.S. Provisional Patent Application No. 62 / 781,253, filed on December 18, 2018, which is incorporated herein by reference in its entirety. Technical Field

[0004] The present invention generally relates to a masking film for protecting sensitive substrates. Background Art

[0005] Masking films, also known as surface protection films, are generally used to provide a physical barrier to prevent damage, contamination, scratching, abrasion and / or other damage to the substrates to which they are attached. Masking films can be applied to delicate, sensitive substrates used as components of electronic displays and protect the substrates during one or more subsequent processing steps during manufacturing and during shipping and / or storage prior to use of the substrates.

[0006] Commonly used masking films achieve adhesion to the substrate through van der Waals forces, which requires that both the masking film and the substrate have at least one very flat and uniform surface so that the masking film can closely contact the substrate. The amount of adhesion can be increased or decreased by softening or hardening the composition on the surface of the masking film. Excessive adhesion makes it difficult to remove the masking film from the substrate at the end of processing. Too little adhesion will cause the masking film to separate from the substrate prematurely and the substrate will no longer be protected.

[0007] In addition, the masking film should adhere to the substrate without damaging the substrate surface during use or during removal of the masking film when it is no longer needed. Some masking films are known to produce textures that alter the image clarity of the substrate that the masking film is supposed to protect from damage. Substrates having surfaces with such textures are known to reflect light in a non-uniform manner and are generally unacceptable when the substrate is used, for example, as a component in an electronic display.

[0008] Adhesive coated oriented polyester films can provide acceptable masking properties for such applications, but are also relatively expensive. Previous efforts to minimize texture that alters image clarity with less expensive polyethylene films have included making both surfaces of the film as smooth as possible and not causing clogging (i.e., sticking) in the wind-up rolls. Reducing the surface roughness of the polyethylene film surface has only achieved minor improvements in the resulting substrate texture.

[0009] It would be desirable to have a masking film that provides the desired surface protection for the substrate without leaving a texture on the substrate and that is more economical than adhesive coated oriented polyester films. Summary of the invention

[0010] It has been surprisingly found that by using a softer polymer formulation and creating at least one surface with a suitable embossed microtexture, damage to delicate substrates can be minimized or even avoided while maintaining sufficient adhesion to the substrate. The combination of softness and microtexture creates a specific type of surface structure that does not affect the image sharpness of the substrate. The surface roughness also does not lead to roll blocking and also improves web handling compared to known films with smooth surfaces.

[0011] According to one aspect of the present invention, a masking film is provided, comprising an adhesive layer comprising a blend of a hydrogenated styrene block copolymer and a low-density polyethylene. The adhesive layer has an outer adhesive surface configured to contact a substrate. The average surface roughness Ra of the outer adhesive surface is 100nm to 350nm, and the average peak spacing Sm is 20μm to 150μm. The masking film also comprises a release layer on the side of the adhesive layer opposite to the outer adhesive surface.

[0012] In one embodiment, the adhesive layer further comprises high density polyethylene.

[0013] In one embodiment, the cling layer blend comprises 15 wt% to 80 wt% of the hydrogenated styrene block copolymer, 5 wt% to 50 wt% of the low density polyethylene, and 10 wt% to 40 wt% of the high density polyethylene.

[0014] In one embodiment, the cling layer blend comprises 40 wt% to 70 wt% of the hydrogenated styrene block copolymer, 5 wt% to 30 wt% of the low density polyethylene, and 10 wt% to 40 wt% of the high density polyethylene.

[0015] In one embodiment, the average surface roughness Ra of the outer adhesive surface is 125 nm to 325 nm, and the average peak spacing Sm is 20 μm to 100 μm.

[0016] In one embodiment, the release layer comprises low density polyethylene. In one embodiment, the release layer comprises a blend of low density polyethylene and high density polyethylene.

[0017] In one embodiment, the masking film further comprises a core layer between the adhesive layer and the release layer. In one embodiment, the core layer comprises a blend of high-density polyethylene and low-density polyethylene. In one embodiment, the core layer blend comprises 30wt% to 50wt% of low-density polyethylene and 50wt% to 70wt% of high-density polyethylene. In one embodiment, the core layer comprises polypropylene.

[0018] Embodiments of the present invention include:

[0019] 1) A masking film comprising:

[0020] An adhesive layer comprising a blend of a hydrogenated styrene block copolymer and a low-density polyethylene, the adhesive layer having an outer adhesive surface configured to contact a substrate, the outer adhesive surface having an average surface roughness Ra of 100 nm to 350 nm, and an average peak spacing Sm of 20 μm to 150 μm; and

[0021] A release layer is on a side of the adhesive layer opposite to the outer adhesive surface.

[0022] 2) The masking film according to embodiment 1, wherein the adhesive layer blend further comprises high density polyethylene.

[0023] 3) The masking film according to embodiment 2, wherein the adhesive layer blend comprises 15 wt% to 80 wt% of hydrogenated styrene block copolymer, 5 wt% to 50 wt% of low density polyethylene and 10 wt% to 40 wt% of high density polyethylene.

[0024] 4) The masking film according to embodiment 3, wherein the adhesive layer blend comprises 40 wt% to 70 wt% of hydrogenated styrene block copolymer, 5 wt% to 30 wt% of low density polyethylene and 10 wt% to 40 wt% of high density polyethylene.

[0025] 5) The masking film according to embodiment 1, wherein the average surface roughness Ra of the outer adhesive surface is 125 nm to 325 nm, and the average peak spacing Sm is 20 μm to 100 μm.

[0026] 6) The masking film according to embodiment 1, wherein the release layer comprises low-density polyethylene.

[0027] 7) The masking film according to embodiment 6, wherein the release layer comprises a blend of low-density polyethylene and high-density polyethylene.

[0028] 8) The masking film according to embodiment 1 further comprises a core layer between the adhesive layer and the release layer.

[0029] 9) A masking film according to embodiment 8, wherein the core layer comprises a blend of high density polyethylene and low density polyethylene.

[0030] 10) A masking film according to embodiment 9, wherein the core layer blend comprises 30 wt% to 50 wt% of low density polyethylene and 50 wt% to 70 wt% of high density polyethylene.

[0031] 11) A masking film according to embodiment 8, wherein the core layer comprises polypropylene.

[0032] These and other aspects, features and characteristics of the present invention, as well as methods of operation and functions of related elements of structure, and combinations of parts, and manufacturing economies, will become clearer by considering the following description and appended claims and with reference to the accompanying drawings, all of which form a part of this specification. However, it is to be expressly understood that the drawings are for illustration and description purposes only and are not intended as a definition of the limits of the invention. As used in the specification and claims, the singular forms "a", "an", and "the" include plural referents unless the context clearly indicates otherwise. BRIEF DESCRIPTION OF THE DRAWINGS

[0033] The components of the following figures are shown to emphasize the general principles of the invention and are not necessarily drawn to scale. For consistency and clarity, reference numerals representing corresponding components are repeated as necessary throughout the drawings.

[0034] Figure 1 schematically shows a masking film according to one embodiment of the present invention; and

[0035] Figure 2 A masking film according to one embodiment of the present invention is schematically shown. DETAILED DESCRIPTION

[0036] As used herein, the term "film" means a sheet or web produced by a cast extrusion or blow molding process. The film of the present invention is made of a polymer. The polymer can be further processed and cooled between rollers to form a web. Multilayer films can be produced by simultaneously extruding different layers in a coextrusion process, or by forming each film layer separately and then combining or laminating the individual films together. In one embodiment, multiple layers of a masking film are coextruded using any coextrusion method known in the art. Using coextrusion can relatively simply and easily manufacture a multilayer masking film comprising different layers, each layer performing a specialized function.

[0037] Figure 1A masking film 100 according to one embodiment of the present invention is schematically shown. As shown, the masking film 100 is a multilayer film that includes an adhesive layer 110 having an outer adhesive surface 112, and a release layer 120 on a side of the adhesive layer 110 opposite the outer adhesive surface 112. The release layer 120 includes an outer release surface 122. The outer adhesive surface 112 of the adhesive layer 110 is configured to contact a substrate surface to be protected by the masking film 100.

[0038] Figure 2 A masking film 200 according to one embodiment of the present invention is schematically shown. As shown, the masking film 200 is a multilayer film that includes an adhesive layer 210 having an outer adhesive surface 212, a release layer 220 on a side of the adhesive layer 210 opposite the outer adhesive surface 212, and a core layer 230 between the adhesive layer 210 and the release layer 220. The release layer 220 includes an outer release surface 222. The outer adhesive surface 212 of the adhesive layer 210 is configured to contact a substrate surface to be protected by the masking film 200.

[0039] Adhesion layer

[0040] As used herein, "adhesion" means adhesion to the substrate surface to be protected by close contact via natural blocking adhesion, which exists between a very smooth surface and another smooth surface via polar bonds, ionic bonds, and in some cases hydrogen bonds and / or van der Waals secondary bonds. Non-adhesive adhesion herein means releasable adhesion, wherein the adhesion is reversible, whereby neither the film nor the substrate to which it is applied is altered or damaged. "Adhesion" does not include materials known as pressure sensitive adhesives, thermal bonding or cross-linking functions of adhesives, because with pressure sensitive adhesives, thermal bonding or cross-linking functions of adhesives, the adhesion between the substrate surface and the film is increased to such a point that the peel strength required to remove the film will exceed the tensile strength of the film itself, thereby causing the film to be torn or broken before it is peeled off from the substrate.

[0041] The adhesive layer 110, 210 according to embodiments of the masking film 110, 200 may include a blend of hydrogenated styrene block copolymer and low density polyethylene (LDPE). In one embodiment, the adhesive layer 110, 210 further includes high density polyethylene (HDPE).

[0042] The hydrogenated block copolymer has a polystyrene block-polydiene block polymer structure before hydrogenation. The hydrogenated block copolymer can be linear or radial before hydrogenation. Suitable polydienes include polybutadiene (1,3-butadiene), polyisoprene, and mixtures thereof. Hydrogenation of the polystyrene block-polydiene block structure produces a styrene ethylene-(butylene / isoprene)-styrene polymer structure, also referred to as "SEBS". See U.S. Patent No. 7,439,301, U.S. Patent No. 7,348,376, U.S. Patent Application Publication No. 2013 / 0225020, International Patent Application Publication No. WO2014 / 087814, and International Patent Application Publication No. WO2014 / 087815 for further description, all of which are incorporated herein by reference in their entirety.

[0043] The styrene content of the hydrogenated styrene block copolymer is desirably less than 40 weight percent (wt%) of the copolymer, such as from about 30 to about 40 wt%, such as 34 wt%.After hydrogenation of the polystyrene block-polydiene block polymer, 0 to 10% of the styrene double bonds in the polystyrene block are hydrogenated.

[0044] The melt flow rate ("MFR") of the hydrogenated styrene block copolymer is negatively correlated with the viscosity of the hydrogenated styrene block copolymer. A high melt flow rate indicates that the styrene block copolymer has a low viscosity, and vice versa. As used herein, unless otherwise specified, "melt index" or MFR shall mean the melt flow value measured at 230°C and 2.16 kg mass according to ASTM D-1238. In one embodiment, the melt index of the hydrogenated styrene block copolymer may be greater than, or equal to, 12. In one embodiment, the melt index of the hydrogenated styrene block copolymer may be greater than, or equal to, 20. In one embodiment, the melt index of the hydrogenated styrene block copolymer may be greater than, or equal to, 40. In one embodiment, the melt index of the hydrogenated styrene block copolymer may be from about 20 to about 100. Suitable hydrogenated styrene block copolymers include Kraton MD 6951 produced by Kraton Performance Polymers Inc., which has a styrene content of about 34 wt% and an MFR of 48.

[0045] The adhesive layer 110, 210 may include 10 wt% to 90 wt% of hydrogenated styrene block copolymer and 10 wt% to 90 wt% of LPDE. In one embodiment, the adhesive layer 110, 210 may include about 60 wt% of hydrogenated styrene block copolymer and about 40 wt% of LDPE, or about 80 wt% of hydrogenated styrene block copolymer and 20 wt% of LPDE. Similarly, the adhesive layer 110, 210 may include a mixture of hydrogenated styrene block copolymer and LDPE in a weight ratio of about 100:0 to 51:49, including, for example, a weight ratio of about 80:20 and about 60:40.

[0046] In various embodiments, the adhesive layer 110, 210 may include 10 wt% to 90 wt% of a hydrogenated styrene block copolymer. In a specific embodiment, the adhesive layer 110, 210 may include 70 wt% to 90 wt% of a hydrogenated styrene block copolymer. In such an embodiment, the adhesive layer 110, 210 may also include 10 wt% to 30 wt% of LDPE, and in a specific embodiment, the adhesive layer 110, 210 may consist essentially of a hydrogenated styrene block copolymer alone.

[0047] In one embodiment, the adhesive layer 110, 210 may include 15wt% to 90wt% of styrene block copolymer (SEBS), 10wt% to 50wt% of LDPE, and 10wt% to 35wt% of HDPE. In one embodiment, the adhesive layer 110, 120 may include 15wt% to 80wt% of hydrogenated styrene block copolymer, 5wt% to 50wt% of low density polyethylene, and 10wt% to 40wt% of high density polyethylene. In one embodiment, the adhesive layer 110, 120 may include 40wt% to 70wt% of hydrogenated styrene block copolymer, 5wt% to 30wt% of low density polyethylene, and 10wt% to 40wt% of high density polyethylene.

[0048] As discussed herein, average surface roughness will be defined as the average height (Ra) (hereinafter referred to as "average surface roughness Ra") of the micro-peaks and micro-valleys from the surface to the center line of the surface, which is measured by a surface photometer. The surface roughness defined in this way is usually expressed in micrometer (μm) units or nanometer (nm) units. In addition, the average spacing (Sm) between the micro-peaks is measured with a surface photometer. The test (relative roughness and peak spacing) of all surface textures is carried out according to ANSI / ASME test method B46.1-1985. According to an embodiment of the present invention, the average surface roughness Ra of the outer adhesive surface 112,212 of the adhesive layer 110,210 is 100nm to 350nm, and the average peak spacing Sm is 20μm to 150μm. In one embodiment, the average surface roughness Ra of the outer adhesive surface 112,212 of the adhesive layer 110,210 is 125nm to 325nm, and the average peak spacing Sm is about 20μm to about 100μm.

[0049] According to an embodiment of the present invention, the thickness of the adhesion layer 110, 210 of the masking film 100, 200 can be 1μm to 20μm, for example, 3μm to 15μm, for example 3μm, 4μm, 5μm, 6μm, 7μm, 8μm, 9μm, 10μm, 11μm, 12μm, 13μm, 14μm, or 15μm.

[0050] Core layer

[0051] The masking film 200 may include an optional core layer 230 such as Figure 2 As shown. The core layer 230, when present, can be adjacently located between the adhesive layer 210 and the release layer 220. The core layer 230, when present, can include one or more polyolefins, such as low density polyethylene (LDPE), linear low density polyethylene (LLDPE), high density polyethylene (HDPE), medium density polyethylene, polypropylene (PP), random copolymer polypropylene, polypropylene impact copolymer, metallocene linear low density polyethylene, plastomer, poly (ethylene-co-vinyl acetate), poly (ethylene-co-acrylic acid), poly (ethylene-co-methyl acrylate), cycloolefin polymer, polyamide, or poly (ethylene-co-butyl acrylate). Suitable polyolefins include low density polyethylene, high density polyethylene, polypropylene, polypropylene impact copolymer, and mixtures thereof. A suitable polyolefin mixture is a mixture of low density polyethylene and high density polyethylene in a weight ratio of 60:40 to 40:60.

[0052] According to an embodiment of the present invention, the thickness of the core layer 230 of the masking film 200 can be 10μm to 50μm, for example 15μm, 16μm, 17μm, 18μm, 19μm, 20μm, 21μm, 22μm, 23μm, 24μm, 25μm, 26μm, 27μm, 28μm, 29μm, 30μm, 31μm, 32μm, 33μm, 34μm, 35μm, 36μm, 37μm, 38μm, 39μm, 40μm, 41μm, 42μm, 43μm, 44μm, 45μm, 46μm, 47μm, 48μm, 49μm, or 50μm.

[0053] Release layer

[0054] The release layer 120, 220 can be adjacent to the adhesive layer 110, 210, or adjacent to the core layer 230 when present. The release layer 120, 220 can include one or more polyolefins, such as low density polyethylene (LDPE), linear low density polyethylene (LLDPE), high density polyethylene (HDPE), medium density polyethylene (MDPE), polypropylene (PP), random copolymer polypropylene, polypropylene impact copolymer, metallocene linear low density polyethylene, plastomer, poly (ethylene-co-vinyl acetate), poly (ethylene-co-acrylic acid), poly (ethylene-co-methyl acrylate), cyclic olefin polymers, polyamides, or poly (ethylene-co-n-butyl acrylate). Suitable polyolefins include low density polyethylene (LDPE), high density polyethylene (HDPE), polypropylene (PP), polypropylene impact copolymer, and mixtures thereof. In one embodiment, the release layer 120, 220 includes a suitable polyolefin mixture of low density polyethylene (LDPE) and high density polyethylene (HDPE) in a weight ratio of 60:40 to 40:60.

[0055] The thickness of the release layer 120, 220 can be 1 μm to 20 μm, such as 1 μm to 10 μm, such as 1 μm, 2 μm, 3 μm, 4 μm, 5 μm, 6 μm, 7 μm, 8 μm, 9 μm, or 10 μm. The relatively rough surface of the release layer 120, 220 typically has an average surface roughness Ra of 0.3 μm to 16 μm, more preferably 0.7 μm to 8 μm.

[0056] Substrate

[0057] Although the masking films 100, 200 of the present invention may be applied to any substrate, typical substrates include, by way of example only, polycarbonates, acrylics, polyvinyl chloride, polyethylene terephthalate (PET), glycol-modified polyethylene terephthalate (PETG), polyimides, glass, ceramics, and metals.

[0058] Application of masking film to substrate

[0059] The multilayer masking film 100, 200 may be applied to the substrate and the applied masking film 100, 200 may be pressed against the smooth surface of the substrate using any of a variety of conventional methods. Generally, the masking film 100, 200 will be removed from a roll and will be applied directly to the substrate by means of a nip roll or similar system through which the masking film 100, 200 and the substrate pass. When the masking film 100, 200 is removed from the roll, the spiral orientation of the masking film 100, 200 on the roll causes the adhesive layer 110, 210 to separate from the release layer 120, 220 when the masking film 100, 200 is removed from the roll.

[0060] Example

[0061] Comparative Example 1 is a prior art masking film made of oriented polyethylene terephthalate (PET) coated with an acrylic adhesive material. The thickness of the PET layer is about 140 μm, and the thickness of the acrylic adhesive layer is about 50 μm.

[0062] Comparative Example 2 is a prior art single-layer masking film made of a blend of low-density polyethylene and a masterbatch containing an antioxidant. The thickness of the single-layer masking film is about 45 μm.

[0063] Comparative Example 3 is a prior art single-layer masking film made of a blend of LDPE and a masterbatch containing an antioxidant. The thickness of the single-layer masking film is about 80 μm.

[0064] Comparative Example 4 is a three-layer masking film having an adhesive layer made of a blend of about 45 wt% hydrogenated styrene block copolymer (SEBS), about 30 wt% HDPE and about 25 wt% LDPE, a core layer made of a blend of about 60 wt% HDPE, about 39 wt% LDPE and about 1 wt% antioxidant masterbatch, and a release layer made of a blend of about 80 wt% LDPE, about 19 wt% HDPE and about 1 wt% antioxidant masterbatch. The thickness of the adhesive layer is about 10.0 μm, the thickness of the core layer is about 32.5 μm, and the thickness of the release layer is about 7.5 μm.

[0065] Example 1 is a three-layer masking film according to one embodiment of the present invention. The three-layer masking film has an adhesive layer made of a blend of about 55 wt% hydrogenated styrene block copolymer (SEBS), about 30 wt% HDPE and about 15 wt% LDPE, a core layer made of a blend of about 55 wt% HDPE and about 45 wt% LDPE, and a release layer made of a blend of about 99 wt% LDPE and about 1 wt% antioxidant-containing masterbatch. The thickness of the adhesive layer is about 4.2 μm, the thickness of the core layer is about 21.0 μm, and the thickness of the release layer is about 2.8 μm.

[0066] Example 2 is a three-layer masking film according to one embodiment of the present invention. The three-layer masking film has an adhesive layer made of a blend of about 60 wt% hydrogenated styrene block copolymer (SEBS), about 25 wt% LDPE and about 15 wt% HDPE, a core layer made of a blend of about 60 wt% HDPE and about 40 wt% LDPE, and a release layer made of a blend of about 60 wt% HDPE and about 40 wt% LDPE. The thickness of the adhesive layer is about 7.5 μm, the thickness of the core layer is about 18.0 μm, and the thickness of the release layer is about 4.5 μm.

[0067] Example 3 is a three-layer masking film according to one embodiment of the present invention. The three-layer masking film has an adhesive layer made of a blend of about 55wt% hydrogenated styrene block copolymer (SEBS), about 30wt% LDPE and about 15wt% HDPE, a core layer made of a blend of about 55wt% HDPE and about 45wt% LDPE, and a release layer made of a blend of about 99wt% LDPE and about 1wt% antioxidant-containing masterbatch. The thickness of the adhesive layer is about 10.0μm, the thickness of the core layer is about 35.0μm, and the thickness of the release layer is about 5.0μm.

[0068] Example 4 is a three-layer masking film according to one embodiment of the present invention. The three-layer masking film has an adhesive layer made of a blend of about 65wt% hydrogenated styrene block copolymer (SEBS), about 30wt% HDPE and about 5wt% LDPE, a core layer made of a blend of about 55wt% HDPE and about 45wt% LDPE, and a release layer made of a blend of about 99wt% LDPE and about 1wt% of an antioxidant-containing masterbatch. The thickness of the adhesive layer is about 10.0μm, the thickness of the core layer is about 35.0μm, and the thickness of the release layer is about 5.0μm.

[0069] Example 5 is a three-layer masking film according to one embodiment of the present invention. The three-layer masking film has an adhesive layer made of a blend of about 48 wt% hydrogenated styrene block copolymer (SEBS), about 30 wt% HDPE and about 22 wt% LDPE, a core layer made of a blend of about 55 wt% HDPE and about 45 wt% LDPE, and a release layer made of a blend of about 99 wt% LDPE and about 1 wt% of an antioxidant-containing masterbatch. The thickness of the adhesive layer is about 13.0 μm, the thickness of the core layer is about 45.5 μm, and the thickness of the release layer is about 6.5 μm.

[0070] Tested the average surface roughness Ra and the average peak spacing Sm and the hardness of each adhesive layer of Comparative Examples 1-4 and Embodiments 1-5. Each of Comparative Examples 1-4 and Embodiments 1-5 is placed on substrate, and the adhesive layer contacts substrate and is peeled off from substrate then. The indication of the texture produced on the adhesion of substrate and substrate is provided by the grade of "low" to "high" and "low" and "high" between "middle". Surface roughness, hardness, the result of the texture produced on the adhesion of substrate and substrate is listed in the following table 1.

[0071] Table I: Adhesion Surface Properties

[0072] sample Ra(nm) Sm(μm) hardness Texture produced on the substrate Adhesion to substrate Comparative Example 1 15 83 Low Low high Comparative Example 2 75 206 high high Low Comparative Example 3 57 248 high middle Low Comparative Example 4 58 101 middle Low high Example 1 318 78 middle Low middle Example 2 145 95 middle Low middle Example 3 126 67 middle Low Low Example 4 139 68 middle Low middle Example 5 282 23 middle Low Low

[0073] It is desirable that the texture produced on the substrate be "low", and Examples 1-5 each meet this criterion. It is also desirable that the adhesion to the substrate be "low" to "medium", and Examples 1-5 each meet this criterion.

[0074] Without being bound by theory, it can be postulated that by using a softer polymer formulation and creating an adhesive surface with an appropriately embossed microtexture, damage to delicate substrates can be minimized or even avoided while maintaining adequate adhesion to the substrate. The combination of softness and microtexture at the adhesive surface creates a specific type of surface structure that does not create undesirable textures on the substrate, such as textures that reduce image clarity. It has been found that, as described above, masking films according to embodiments of the present invention significantly increase the image clarity of the substrate to which the masking film is adhered, compared to prior art masking films.

[0075] The embodiments herein represent many possible embodiments and examples, and are not intended to necessarily limit the present invention to any specific embodiment. On the contrary, these embodiments may be subjected to different changes, as will be appreciated by those skilled in the art. Any such change is intended to be included in the spirit and scope of the present invention and is protected by the appended claims.

Claims

1. A masking film comprising: An adhesive layer comprising a blend of 40 wt % to 70 wt % of a hydrogenated styrene block copolymer, 5 wt % to 30 wt % of a low density polyethylene, and 10 wt % to 40 wt % of a high density polyethylene, the adhesive layer having an outer adhesive surface configured to reversibly contact a substrate so that the substrate is not altered or damaged, the outer adhesive surface having an average surface roughness Ra of 125 nm to 325 nm, and an average peak spacing Sm of 20 μm to 100 μm, as measured with a profilometer according to ANSI / ASME Test Method B46.1-1985; a release layer on a side of the adhesive layer opposite the outer adhesive surface; and The core layer is located between the adhesive layer and the release layer. The masking film according to claim 1 , wherein the release layer comprises low-density polyethylene.

3. The masking film of claim 2, wherein the release layer comprises a blend of low-density polyethylene and high-density polyethylene.

4. The masking film of claim 1 wherein the core layer comprises a blend of high density polyethylene and low density polyethylene.

5. The masking film of claim 4, wherein the core layer blend comprises 30 wt% to 50 wt% low density polyethylene and 50 wt% to 70 wt% high density polyethylene. The masking film of claim 1 , wherein the core layer comprises polypropylene.

7. The masking film according to claim 1, wherein the hydrogenated styrene block copolymer has a styrene content of less than 40 wt%.

8. The masking film according to claim 7, wherein the styrene content of the hydrogenated styrene block copolymer is 30 wt% to 40 wt%. 9 . The masking film according to claim 1 , wherein a thickness of the adhesive layer is 1 μm to 20 μm.

10. The masking film of claim 1, wherein the thickness of the core layer is 10 μm to 50 μm. The masking film according to claim 1 , wherein a thickness of the release layer is 1 μm to 20 μm.

12. The masking film of claim 1 , wherein the core layer comprises one or more of: low density polyethylene, linear low density polyethylene, high density polyethylene, medium density polyethylene, polypropylene, random copolymer polypropylene, polypropylene impact copolymer, metallocene linear low density polyethylene, plastomers, poly(ethylene-co-vinyl acetate), poly(ethylene-co-acrylic acid), poly(ethylene-co-methyl acrylate), cycloolefin polymers, polyamides, or poly(ethylene-co-n-butyl acrylate).

13. The masking film of claim 4, wherein for the core layer, the weight ratio of low density polyethylene to high density polyethylene ranges from 60:40 to 40:

60.

14. The masking film of claim 1, wherein the release layer comprises one or more of: low density polyethylene, linear low density polyethylene, high density polyethylene, medium density polyethylene, polypropylene, random copolymer polypropylene, polypropylene impact copolymer, metallocene linear low density polyethylene, plastomers, poly(ethylene-co-vinyl acetate), poly(ethylene-co-acrylic acid), poly(ethylene-co-methyl acrylate), cycloolefin polymers, polyamides, or poly(ethylene-co-n-butyl acrylate).

15. The masking film of claim 3, wherein for the release layer, a weight ratio of low density polyethylene to high density polyethylene is in the range of 60:40 to 40:

60. The masking film according to claim 1 , wherein an average surface roughness Ra of the release layer is 0.3 μm to 16 μm.

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